REGENERATION III 



tends to inhibit the formation or persistence of an extra holdfast, 

 and second, that free posterior ends of one or more stripes in the 

 ramifying zone are inductive of tail formation. 



Surprisingly, a new posterior pole and holdfast can be formed 

 in a way which one would never expect to occur in the usual life 

 of stentors (Tartar, 1956b). As Balbiani had noticed, longitudinal 

 aboral halves tend to fold on themselves to close the wound, and if 

 this situation persists, a new pole is formed at the point of bending. 

 There one observes that the pigment stripes are severed just as in 

 the formation of a division furrow, the cut ends of these, and 

 doubtless of the fibrous alternating clear bands as well, are then 

 brought together at a point from which a holdfast emerges (Fig. 27). 

 Sometimes when the original half-holdfast persisted and moved 

 posteriorly to a more normal location, it was nevertheless later 

 resorbed and replaced by the new organelle produced in such an 

 odd manner. 



A stentor with single head but two tail poles and holdfasts, 

 like a specimen found in nature by Faure-Fremiet (1906), was 

 produced when Balbiani (1891b) split the posterior end. This 

 dupHcation can also be produced in Condylostoma (Tartar, 1941b), 

 but in either genus it is much more usual for the two parts simply 

 to fuse together again. 



(c) Reconstitution of the normal shape 



Examples already given are enough to indicate the strong 

 tendency of stentors to reconstitute the normal shape and contour 

 of the cell. Later discussions will show that this capacity is indeed 

 phenomenal, though easily passed over because of the slow pace 

 with which it is pursued. For the present it is sufficient to say that 

 no shape distortion of a stentor has yet been produced from which 

 the animal could not recover in time. The gradual nature of the 

 processes involved was emphasized by Schwartz (1935), who 

 showed that minor discrepancies in the striping persisted for a 

 long time. 



Apart from such minute disruptions, the shape of a stentor 

 seems to be strictly a function of the pattern of the striping 

 (Tartar, 1954). When from aborted cleavage or for some other 

 reason there is a break in the striping, the contour of the cell 

 shows a corresponding deviation from normal (Fig. 28A) and if the 



